Furan-containing flame retardant molecules

ABSTRACT

A furan-containing flame retardant molecule includes a furan moiety bonded to a phosphorus moiety via a phosphoryl linkage or via a phosphinyl linkage.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims priority fromU.S. patent application Ser. No. 15/375,362, filed on Dec. 12, 2016.

BACKGROUND

Plastics are typically derived from a finite and dwindling supply ofpetrochemicals, resulting in price fluctuations and supply chaininstability. Replacing non-renewable petroleum-based polymers withpolymers derived from renewable resources may be desirable. However,there may be limited alternatives to petroleum-based polymers in certaincontexts. To illustrate, particular plastics performance standards maybe specified by a standards body or by a regulatory agency. In somecases, alternatives to petroleum-based polymers may be limited as aresult of challenges associated with satisfying particular plasticsperformance standards.

SUMMARY

In a particular embodiment, a furan-containing flame retardant moleculeis disclosed. The furan-containing flame retardant molecule includes afuran moiety bonded to a phosphorus moiety via a phosphoryl linkage orvia a phosphinyl linkage.

In another embodiment, a process of forming a furan-containing flameretardant molecule is disclosed. The furan-containing flame retardantmolecule includes a furan moiety bonded to a phosphorus moiety via aphosphoryl linkage or via a phosphinyl linkage.

In yet another embodiment, a process of forming a furan-containing flameretardant molecule from furfuryl alcohol is disclosed. Thefuran-containing flame retardant molecule includes a methylfuran groupbonded to a phosphorus moiety via a phosphoryl linkage or via aphosphinyl linkage.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing examples of furan-containing flame retardantmolecules, according to one embodiment.

FIG. 2 is a chemical reaction diagram showing a process of forming thefirst furan-containing flame retardant molecule depicted in FIG. 1,according to one embodiment.

FIGS. 3A and 3B are chemical reaction diagrams showing alternativeembodiments of processes of forming the second furan-containing flameretardant molecule depicted in FIG. 1.

FIGS. 4A and 4B are chemical reaction diagrams showing alternativeembodiments of processes of forming the third furan-containing flameretardant molecule depicted in FIG. 1.

FIGS. 5A and 5B are chemical reaction diagrams showing alternativeembodiments of processes of forming the fourth furan-containing flameretardant molecule depicted in FIG. 1.

FIG. 6 is a chemical reaction diagram showing a particular embodiment ofa process of utilizing the first furan-containing flame retardantmolecule depicted in FIG. 1 to form a cross-linkable flame retardantmaterial.

FIG. 7 is a chemical reaction diagram showing a particular embodiment ofa process of utilizing the second furan-containing flame retardantmolecule depicted in FIG. 1 to form a cross-linkable flame retardantmaterial.

FIG. 8 is a chemical reaction diagram showing a particular embodiment ofa process of utilizing the third furan-containing flame retardantmolecule depicted in FIG. 1 to form a cross-linkable flame retardantmaterial.

FIG. 9 is a chemical reaction diagram showing a particular embodiment ofa process of utilizing the fourth furan-containing flame retardantmolecule depicted in FIG. 1 to form a cross-linkable flame retardantmaterial.

FIG. 10 is a chemical reaction diagram showing a particular embodimentof a process of utilizing the first furan-containing flame retardantmolecule of FIG. 1 to form a cross-linkable flame retardant particle(CLFRP).

FIG. 11 is a diagram showing an example of a dienophile-functionalizedparticle that may be reversibly cross-linked to the CLFRP of FIG. 10 viaa Diels-Alder reaction.

FIG. 12 is a flow diagram showing a particular embodiment of a processof forming a cross-linkable flame retardant polymeric material from afuran-containing flame retardant molecule.

FIG. 13 is a flow diagram showing a particular embodiment of a processof forming a cross-linkable flame retardant particle from afuran-containing flame retardant molecule.

DETAILED DESCRIPTION

The present disclosure describes furan-containing flame retardant (FR)molecules and methods of forming furan-containing FR molecules. Thepresent disclosure also describes applications of the furan-containingFR molecules. The furan-containing FR molecules of the presentdisclosure include at least one furan moiety bonded to a phosphorusmoiety via a phosphoryl linkage or via a phosphinyl linkage. Bonding thephosphorus moiety to the furan moiety (or moieties) imparts flameretardant characteristics to the molecules. Further, when thefuran-containing FR molecules are incorporated into a polymeric materialor bonded to a particle, each furan moiety represents a diene group thatmay be used for subsequent cross-linking (e.g., via a Diels-Alderreaction with a dienophile-functionalized material).

The furan-containing FR molecules of the present disclosure may besynthesized from furfuryl alcohol. Furfuryl alcohol represents arenewable feedstock material that may be synthesized from biomass (e.g.,via catalytic reduction of furfural derived from corn stover and/orsugar cane bagasse). Accordingly, the furan-containing FR molecules ofthe present disclosure may be used to increase the renewable content ina polymeric material, while simultaneously imparting flame retardantcharacteristics and potentially reducing or eliminating the need forflame retardant additives.

The furfuryl alcohol-derived furan-containing FR molecules of thepresent disclosure are synthesized to incorporate a phosphorus group inorder to impart flame retardant properties. The furfuryl alcohol-derivedfuran-containing FR molecules of the present disclosure may have one ortwo furan moieties in order to allow for variable control over thepotential extent of subsequent cross-linking. When the furan moiety is amethylfuran group, each furan moiety can either be linked to thephosphorus moiety directly through the methylene carbon via aphosphinate linkage (a C—P linkage, also referred to as a phosphinyllinkage) or through the oxygen of furfuryl alcohol via a phosphatelinkage (a C—O—P linkage, also referred to as a phosphoryl linkage).

In some cases, the furan-containing FR molecules of the presentdisclosure may be utilized to form a cross-linkable flame retardant(CLFR) polymeric/oligomeric material. In other cases, thefuran-containing FR molecules of the present disclosure may be utilizedto form a cross-linkable flame retardant particle (CLFRP). In bothcases, the furan moieties represent available cross-linking locations(e.g., for reversibly cross-linking to a renewable/non-renewablepolymeric material or to a dienophile-functionalized particle). Further,in the case of CLFRPs, rather than adding separate silica particles andflame retardant particles/molecules, the flame retardant moiety isbonded to the particle itself.

Referring to FIG. 1, a diagram 100 illustrates examples offuran-containing FR molecules according to the present disclosure. FIG.1 illustrates four examples of furan-containing FR molecules thatinclude one or more furan moieties bonded to a phosphorus moiety via oneor more phosphoryl linkages or via one or more phosphinyl linkages. Asdescribed further herein, the furan-containing FR molecules illustratedin FIG. 1 may be formed from renewable furfuryl alcohol.

In FIG. 1, a first furan-containing FR molecule (identified as“Furan-Containing FR Molecule(1)” in FIG. 1) includes two furan moieties(e.g., two methylfuran groups) and a chloride group. A secondfuran-containing FR molecule (identified as “Furan-Containing FRMolecule(2)” in FIG. 1) includes one furan moiety (e.g., one methylfurangroup) and a chloride group. The first furan-containing FR molecule ofFIG. 1 and the second furan-containing FR molecule depicted in FIG. 1represent examples of molecules having one or more furan moieties bondedto a phosphorus moiety via phosphoryl linkages (i.e., via the oxygenfrom the furfuryl alcohol precursor). The first furan-containing FRmolecule of FIG. 1 represents a difuran-functionalized phosphatemolecule, having two furan moieties (e.g., methylfuran groups) bonded tothe phosphorus moiety via phosphoryl linkages. The secondfuran-containing FR molecule of FIG. 1 represents amonofuran-functionalized phosphate molecule, having a single furanmoiety (e.g., a single methylfuran group) bonded to the phosphorusmoiety via a phosphoryl linkage. The number of furan moieties representsthe number of potential cross-linking locations. As described furtherherein, a single furan moiety provides a single potential cross-linkinglocation, and two furan moieties provide two potential cross-linkinglocations (e.g., via a Diels-Alder reaction with adienophile-functionalized material).

In FIG. 1, a third furan-containing FR molecule (identified as“Furan-Containing FR Molecule(3)” in FIG. 1) includes two furan moieties(e.g., two methylfuran groups) and a chloride group. A fourthfuran-containing FR molecule (identified as “Furan-Containing FRMolecule(4)” in FIG. 1) includes a single furan moiety (e.g., a singlemethylfuran group) and a chloride group. The third furan-containing FRmolecule of FIG. 1 and the fourth furan-containing FR molecule depictedin FIG. 1 represent examples of molecules having one or more furanmoieties bonded to a phosphorus moiety via phosphinyl linkages. Thethird furan-containing FR molecule of FIG. 1 represents adifuran-functionalized phosphonate molecule, having two furan moieties(e.g., methylfuran groups) bonded to the phosphorus moiety viaphosphinyl linkages. The fourth furan-containing FR molecule of FIG. 1represents a monofuran-functionalized phosphonate molecule, having asingle furan moiety (e.g., a single methylfuran group) bonded to thephosphorus moiety via a phosphinyl linkage.

The first furan-containing FR molecule of FIG. 1 may be formed accordingto the process described further herein with respect to FIG. 2. In somecases, as described further herein with respect to FIG. 6, the two furanmoieties may be used to form two terminal furan moieties at each end ofa cross-linkable flame retardant (CLFR) oligomer/polymer. Each terminalfuran moiety represents a diene group that may (reversibly) react with adienophile group of another material via a Diels-Alder reaction. Inother cases, as described further herein with respect to FIG. 10, thefirst furan-containing FR molecule of FIG. 1 may be used to form a CLFRparticle (CLFRP) having two furan moieties bonded to a surface of ahydroxyl-containing particle (e.g., a silica particle) via a chemicalreaction of the chloride group and the hydroxyl group. As shown in theexample of FIG. 11, the two furan moieties of the CLFRP represent twopotential locations for cross-linking reactions with dienophile groupsof a dienophile-functionalized particle.

In some cases, the second furan-containing FR molecule of FIG. 1 may beformed according to the process described further herein with respect toFIG. 3A. In other cases, the second furan-containing FR molecule of FIG.1 may be formed according to the process described further herein withrespect to FIG. 3B. As described further herein with respect to FIG. 7,the single furan moiety may be used to form a single terminal furanmoiety at each end of a CLFR oligomer/polymer. The terminal furan moietyrepresents a diene group that may (reversibly) react with a dienophilegroup of another material via a Diels-Alder reaction. In other cases,the second furan-containing FR molecule of FIG. 1 may be used to form aCLFRP having one furan moiety bonded to a surface of ahydroxyl-containing particle (e.g., a silica particle) via a chemicalreaction of the chloride group and the hydroxyl group. The single furanmoiety of the CLFRP represents one potential location for a reversiblecross-linking reaction with a dienophile group of adienophile-functionalized material (e.g., a dienophile-functionalizedparticle in the example of FIG. 11).

In some cases, the third furan-containing FR molecule of FIG. 1 may beformed according to the process described further herein with respect toFIG. 4A. In other cases, the third furan-containing FR molecule of FIG.1 may be formed according to the process described further herein withrespect to FIG. 4B. In some cases, as described further herein withrespect to FIG. 8, the two furan moieties may be used to form twoterminal furan moieties at each end of a CLFR oligomer/polymer. Eachterminal furan moiety represents a diene group that may (reversibly)react with a dienophile group of another material via a Diels-Alderreaction. In other cases, the third furan-containing FR molecule of FIG.1 may be used to form a CLFRP, having two furan moieties, bonded to asurface of a hydroxyl-containing particle (e.g., a silica particle) viaa chemical reaction of the chloride group and the hydroxyl group. Thetwo furan moieties of the CLFRP represent two potential locations forreversible cross-linking reactions with dienophile groups of adienophile-functionalized material (e.g., a dienophile-functionalizedparticle in the example of FIG. 11).

In some cases, the fourth furan-containing FR molecule of FIG. 1 may beformed according to the process described further herein with respect toFIG. 5A. In other cases, the fourth furan-containing FR molecule of FIG.1 may be formed according to the process described further herein withrespect to FIG. 5B. As described further herein with respect to FIG. 9,the single furan moiety may be used to form a single terminal furanmoiety at each end of a CLFR oligomer/polymer. The terminal furan moietyrepresents a diene group that may (reversibly) react with a dienophilegroup of another material via a Diels-Alder reaction. In other cases,the fourth furan-containing FR molecule of FIG. 1 may be used to form aCLFRP, having one furan moiety, bonded to a surface of ahydroxyl-containing particle (e.g., a silica particle) via a chemicalreaction of the chloride group and the hydroxyl group. The single furanmoiety of the CLFRP represents one potential location for a reversiblecross-linking reaction with a dienophile group of adienophile-functionalized material (e.g., a dienophile-functionalizedparticle in the example of FIG. 11).

Thus, FIG. 1 illustrates examples of furan-containing FR molecules thatinclude one or more furan moieties bonded to a phosphorus moiety via oneor more phosphoryl linkages or via one or more phosphinyl linkages. FIG.1 illustrates that the furan-containing FR molecule can either possessone or two furan moieties in order to allow for variable control overthe potential extent of subsequent cross-linking, as described furtherherein.

Referring to FIG. 2, a chemical reaction diagram 200 illustrates anexample of a process of forming the first furan-containing flameretardant molecule depicted in FIG. 1, according to one embodiment. FIG.2 illustrates that the first furan-containing FR molecule depicted inFIG. 1 may be synthesized from the renewable furan moiety, furfurylalcohol.

FIG. 2 illustrates an example of a process of forming adifuran-functionalized phosphate molecule from furfuryl alcohol. In thefirst chemical reaction depicted in FIG. 2, furfuryl alcohol ischemically reacted with phosphorus trichloride (PCl₃) to form aphosphine oxide intermediate material. As an example, the first chemicalreaction may include dissolving phosphorus oxychloride in a suitablesolvent, such as dichloromethane (DCM), with the reaction proceedingfrom 0° C. to room temperature. As a prophetic example, phosphorustrichloride and DCM may be placed in a flask immersed in an ice bath andequipped with a magnetic stirrer and a condenser (the head of which isconnected to a water vacuum pump). Furfuryl alcohol, diluted with DCMmay be added dropwise to the mixture. The mixture may be stirred foranother 10 minutes, and DCM may be subsequently evaporated.

As a prophetic example, PCl₃ (1.0 eq.) and freshly dried toluene may beadded to a two-necked round-bottom flask flushed with inert gas. Thereaction mixture may be stirred at 0° C. Furfuryl alcohol (2.0 eq.),dimethylphenylamine (2.16 eq.), and toluene may be added to a separatetwo-necked round-bottom flask flushed with inert gas. The furfurylalcohol mixture may be added dropwise to the PCl₃ solution over 1 hour.The resulting mixture may be stirred at ambient temperature for 1additional hour. Upon completion, water may be added carefully and themixture may be stirred for 30 min at ambient temperature. The crudeproduct may be extracted with Et₂O (2×) and washed wish water (2<). Theorganic phase may be dried (MgSO₄) and the solvent may be removed invacuo, and may be dried or purified further.

In the second chemical reaction depicted in FIG. 2, the phosphine oxideintermediate material is chemically reacted with either isocyanuricchloride or tert-butyl hypochlorite (tBuOCl) to formbis(furylmethylene)phosphoryl chloride, corresponding to the firstfuran-containing FR molecule of FIG. 1. In the case of isocyanuricchloride, the second chemical reaction may include a suitable solventsuch as acetonitrile (MeCN). In the case of tert-butyl hypochlorite, thesecond chemical reaction may include a suitable solvent such as DCM.FIG. 2 illustrates that the resulting molecule has a functionalphosphorus group with two furan groups available for subsequentreversible cross-linking.

As a prophetic example (using isocyanuric chloride),bis(furan-2-ylmethyl) phosphite (1.0 eq.) in either dry acetonitrile(MeCN), toluene, or dichloromethane (DCM) may be added to a solution oftrichloroisocyanuric acid (0.33 eq.), N-chlorosuccinimide (1.0 eq.), ortert-butyl hypochlorite (1.0 eq.) in the same solvent at roomtemperature, under an N₂ atmosphere. Upon the formation of aprecipitate, the reaction may be stirred at room temperature for anadditional 2 hours. Upon completion of the reaction, as determined by³¹P NMR, the reaction mixture was passed through a 0.45 μm Whatmansyringe filter and concentrated under vacuum. A similar procedure may beutilized in the case of tert-butyl hypochlorite.

Thus, FIG. 2 illustrates an example of a process of forming afuran-containing FR molecule from renewable furfuryl alcohol. In theexample of FIG. 2, furfuryl alcohol is used to form a furan-containingFR molecule having two furan moieties bonded to a phosphorus moiety viatwo phosphoryl linkages. As described further herein, the phosphorusmoiety includes a chloride group for bonding (e.g., via chemicalreaction with a hydroxyl group), and the two furan moieties provide twopotential locations for Diels-Alder reactions with dieonophile group(s)of another material.

FIGS. 3A and 3B are chemical reaction diagrams showing alternativeembodiments of processes of forming the second furan-containing flameretardant molecule depicted in FIG. 1. Referring to FIG. 3A, a firstchemical reaction diagram 300 illustrates a first embodiment of aprocess of forming the second furan-containing flame retardant moleculedepicted in FIG. 1. Referring to FIG. 3B, a second chemical reactiondiagram 310 illustrates an alternative embodiment of a process offorming the second furan-containing flame retardant molecule depicted inFIG. 1.

FIG. 3A illustrates a first example of a process of forming amonofuran-functionalized phosphonate molecule. FIG. 3A illustrates aone-step process via reaction of furfuryl alcohol with dichlorophosphatevia careful addition and stoichiometric control. The alkyl (R) groupsmay include ethyl groups, methyl groups, propyl groups, isopropylgroups, or phenyl groups, among other alternatives. The one-step processmay utilize triethylamine (Et₃N) and a suitable solvent, such astetrahydrofuran (THF), and the chemical reaction may be performed from0° C. to room temperature. FIG. 3A illustrates that the resultingmolecule is functionalized with one furan moiety for cross-linking andone chloride for further bonding.

As a prophetic example, to a stirred solution that may include furfurylalcohol (1.0 eq.) and triethylamine (2.0 eq.) in anhydrous THF, phenyldichlorophosphate (1.3 eq.) may be added dropwise at 0° C., and thereaction mixture may be stirred at ambient temperature for 2 hours or itmay be heated up to reflux (60-65° C.) for an extended reaction time (4hours). The reaction mixture may be cooled to ambient temperature andfiltered to remove the triethylamine hydrochloride salt. The solvents ofthe filtrate may be removed in vacuo and the product may be purified byfractional distillation.

FIG. 3B illustrates a second example of a process of forming themonofuran-functionalized phosphate molecule. FIG. 3B illustrates analternative in which furfuryl alcohol can be reacted with titanium (IV)isopropoxide and phophonic acid dialkylester or diphenylester as apseudotransesterification. The R groups may include ethyl groups, methylgroups, propyl groups, isopropyl groups, or phenyl groups, among otheralternatives. The resulting molecule may be reacted with thionylchloride to give a furan-containing FR molecule with one furan moietyfor cross-linking and one chloride for further bonding. In the firstchemical reaction, titanium (IV) isopropoxide may be dissolved in asuitable solvent, such as benzene. In the second chemical reaction,thionyl chloride may be dissolved in a suitable solvent, such as carbontetrachloride (CCl₄), and the chemical reaction may be performed from 0°C. to room temperature.

As a prophetic example, Dialkyl or diaryl phosphite 1 (5.5 mmol) may beadded to the solution of the titanium (IV) isopropoxide (11 mmol) infurfuryl alcohol (excess). This solution may be diluted with benzene.The reaction mixture may be heated 40° C. until completion. The mixturemay be poured into water, extracted with CH₂Cl₂ (3×), dried over MgSO₄,and solvent and volatile components may be removed in vacuo. Theproducts may be purified by fractional distillation orrecrystallization. The product from the first step (1.0 eq.), in dryacetonitrile (MeCN), toluene, or dichloromethane (DCM), may be added toa solution of trichloroisocyanuric acid (0.33 eq.), N-chlorosuccinimide(1.0 eq.), or tert-butyl hypochlorite (1.0 eq.) in the same solvent atroom temperature, under an N₂ atmosphere. Upon the formation of aprecipitate, the reaction may be stirred at room temperature for anadditional 2 hours. Upon completion of the reaction, as determined by³¹P NMR, the reaction mixture may be passed through a 0.45 μm Whatmansyringe filter and concentrated under vacuum.

FIGS. 3A and 3B illustrate examples of alternative processes of forminga furan-containing flame retardant molecule from renewable furfurylalcohol. In the examples of FIGS. 3A and 3B, furfuryl alcohol is used toform a furan-containing FR molecule having a single furan moiety bondedto a phosphorus moiety via a phosphoryl linkage. As described furtherherein, the phosphorus moiety includes a chloride group for bonding(e.g., via chemical reaction with a hydroxyl group), and the singlefuran moiety provides one potential location for a Diels-Alder reactionwith a dienophile group of another material.

FIGS. 4A and 4B are chemical reaction diagrams showing alternativeembodiments of processes of forming the third furan-containing FRmolecule depicted in FIG. 1. Referring to FIG. 4A, a first chemicalreaction diagram 400 illustrates a first embodiment of a process offorming the third furan-containing FR molecule depicted in FIG. 1.Referring to FIG. 4B, a second chemical reaction diagram 410 illustratesan alternative embodiment of a process of forming the thirdfuran-containing FR molecule depicted in FIG. 1.

FIG. 4A illustrates a first example of a process of forming abisfuran-functionalized phosphine oxide molecule. In the first chemicalreaction depicted in FIG. 4A, furfuryl alcohol is chemically reactedwith thionyl chloride to form 2-(chloromethyl)furan, and the chemicalreaction may be performed from 0° C. to room temperature. Alternatively,bromomethylfuran can be synthesized from commercially available reagentsand can be used similarly to chloromethylfuran. In the second chemicalreaction depicted in FIG. 4A, a Grignard reagent is prepared and reactedwith the appropriate phosphonic acid diester to form a phosphinic acidintermediate material. In the third chemical reaction of FIG. 4A, thephosphinic acid intermediate material is reacted with thionyl chloride,resulting in the third furan-containing FR molecule of FIG. 1.

As a prophetic example, furfuryl alcohol may be added, dropwise, to anexcess of thionyl chloride at 0° C. The reaction mixture may be warmedto ambient temperature or reflux and stirred until completion asindicated by TLC. The excess thionyl chloride may be removed in vacuoand the crude product may be used in the next step without furtherpurification. To a stirred suspension of activated magnesium turnings indiethyl ether may be added 2-chloromethylfuran, dropwise, at 0° C. Uponcompletion of the addition, the reaction mixture may be heated to refluxfor 1 hour. The reaction mixture is then cooled to room temperature andmay be added via cannula to a stirred solution of phosphonic aciddiethyl ester at 0° C. The reaction mixture may be warmed to roomtemperature and stirred until completion, poured into water, andextracted with diethyl ether. The combined organic fractions may bedried over MgSO₄, filtered, and the solvents removed in vacuo. Theproduct may be purified by distillation or recrystallization. Thephosphine oxide product may be added to a suspension of PhIO in anorganic solvent that may include THF or toluene. The reaction mixturemay be stirred for 20 minutes to 12 hours at reflux. The reactionmixture may then be diluted with ether and extracted of 5% NaHCO₃ watersolution. The organic layer may be dried over MgSO₄, evaporated andseparated by chromatography. The water layer may be acidified with conc.HCl and extracted with ether. The combined ether solutions may be driedover MgSO₄, filtered and evaporated to yield the product. Thebis(methyl)furan phosphine oxide may be added, dropwise, to an excess ofthionyl chloride (or oxalyl chloride, or isocyanuric chloride) at 0° C.The reaction mixture may be warmed to ambient temperature or reflux andstirred until completion as indicated by TLC. The excess thionylchloride may be removed in vacuo and the crude product may be purifiedby fractional distillation.

FIG. 4B illustrates a second example of a process of forming thebisfuran-functionalized phosphine oxide molecule. In the first chemicalreaction depicted in FIG. 4A, furfuryl alcohol is chemically reactedwith thionyl chloride to form 2-(chloromethyl)furan, and the chemicalreaction may be performed from 0° C. to room temperature. Alternatively,bromomethylfuran can be synthesized from commercially available reagentsand can be used similarly to chloromethylfuran. In the second chemicalreaction depicted in FIG. 4B, the 2-(chloromethyl)furan product formedfrom the furfuryl alcohol may be used to form a phosphinic esterintermediate material. The third chemical reaction of FIG. 4Billustrates that the phosphinic ester intermediate material is reactedwith phosphorus pentachloride (PCl₅), resulting in the thirdfuran-containing FR molecule of FIG. 1.

As a prophetic example, to a stirred suspension of activated magnesiumturnings in diethyl ether may be added 2-chloromethylfuran (synthesizedas described previously), dropwise, at 0° C. Upon completion of theaddition, the reaction mixture may be heated to reflux for 1 hour. Thereaction mixture is then cooled to room temperature and may be added viacannula to a stirred solution of phosphonic acid diethyl ester at 0° C.The reaction mixture may be warmed to room temperature and stirred untilcompletion, poured into water, and extracted with diethyl ether. Thecombined organic fractions may be dried over MgSO₄, filtered, and thesolvents removed in vacuo. The product may be purified by distillationor recrystallization. The phosphinic acid product may be stirred with asuspension of potassium carbonate in an organic solvent such as DMF orTHF and heated to a temperature that may be between 60-100° C. Methyliodide and 18-crown-6 may be added dropwise to the reaction mixture, andmay be stirred until completion. The reaction mixture may be poured intowater, and extracted with diethyl ether. The combined organic fractionsmay be dried over MgSO₄, filtered, and the solvents removed in vacuo.The product may be purified by distillation or recrystallization. To asolution of the product from the previous step in CCl₄ may be added PCl₅(excess) at 0° C. under an inert atmosphere. The mixture may be allowedto warm up to room temperature and may be stirred for an additional day.The solvent is removed in vacuo and the residue may be distilled to givethe product.

Thus, FIGS. 4A and 4B illustrate alternative processes of forming afuran-containing flame retardant molecule from renewable furfurylalcohol. In the examples of FIGS. 4A and 4B, furfuryl alcohol is used toform a furan-containing FR molecule having two furan moieties bonded toa phosphorus moiety via two phosphinyl linkages. As described furtherherein, the phosphorus moiety includes a chloride group for bonding(e.g., via chemical reaction with a hydroxyl group), and the two furanmoieties provide two potential locations for Diels-Alder reactions withdieonophile group(s) of another material.

FIGS. 5A and 5B are chemical reaction diagrams showing alternativeembodiments of processes of forming the fourth furan-containing FRmolecule depicted in FIG. 1. Referring to FIG. 5A, a first chemicalreaction diagram 500 illustrates a first embodiment of a process offorming the fourth furan-containing FR molecule depicted in FIG. 1.Referring to FIG. 5B, a second chemical reaction diagram 510 illustratesan alternative embodiment of a process of forming the fourthfuran-containing FR molecule depicted in FIG. 1.

FIG. 5A illustrates a first example of a process of forming the singlephosphonate-linked furan phosphoryl chloride, methylenefuran-phosphonylchloride. In the first chemical reaction depicted in FIG. 5A,2-(chloromethyl)furan (which may be synthesized as described herein withrespect to FIGS. 4A and 4B) is chemically reacted with atrialkylphosphite or a triphenylphosphite to form a phosphonyl ester. Rgroups may include ethyl groups, methyl groups, propyl groups, isopropylgroups, or phenyl groups, among other alternatives. In the secondchemical reaction depicted in FIG. 5B, the phosphonyl ester is reactedwith phosphorus pentachloride to form the fourth furan-containing FRmolecule depicted in FIG. 1.

As a prophetic example, 2-(chloromethyl)furan (1 eq.) and trialkylphosphite may be added to a reaction vessel, which may include anorganic solvent such as toluene, THF, ethanol, or DMF, and may alsocontain a compound such an alumina. The reaction may be heated to refluxor up to 180° C. if done using neat conditions. The reaction mixture mayalso be irradiated by microwaves for a short period to increase thereaction rate. The reaction may be cooled to room temperature and theexcess trialky phosphite may be removed in vacuo or it may be washedwith DCM, and dried for CaCl₂) prior to filtration and having thesolvents removed in vacuo. The phosphonate may be purified by fractionaldistillation. To a solution of the phosphonate product may be added PCl₅(excess) at 0° C. under an inert atmosphere. The reaction may beperformed in a solvent such as CCl₄. The mixture may be allowed to warmup to room temperature and may be stirred for an additional day. Thesolvent is removed in vacuo and the residue may be distilled to give theproduct.

FIG. 5B illustrates a second example of a process of forming the singlephosphonate-linked furan phosphoryl chloride, methylenefuran-phosphonylchloride. In the first chemical reaction depicted in FIG. 5B,2-(chloromethyl)furan (synthesized as described herein with respect toFIGS. 4A and 4B) is reacted with a trialkylphosphite or atriphenylphosphite and quenching under aqueous basic conditions to forman alternative intermediate material. R groups may include ethyl groups,methyl groups, propyl groups, isopropyl groups, or phenyl groups, amongother alternatives. The second chemical reaction of FIG. 5B illustratesthat the intermediate material is then reacted with thionyl chloride toform the fourth furan-containing FR molecule depicted in FIG. 1.

As a prophetic example, a methylfuryl phosphonate may be generated in amanner similar to that of the phosphonate intermediate used tosynthesize the fourth furan-containing FR molecule. Dialkylbenzylphosphonate (1.0 eq.) may be quickly added to a solution ofbromodimethyl borane (1.0 eq.) in an organic solvent that may betoluene. The reaction mixture may be warmed to room temperature andstirred overnight. The solvent and volatile byproducts may be removed invacuo and give a slightly yellow viscous oil. To a solution of thephosphonic acid product may be added SOCl₂ (excess) at 0° C. The mixturemay be allowed to warm up to room temperature, or heated to 40° C. andmay be stirred for an additional day. The solvent is removed in vacuoand the residue may be distilled to give the product.

Thus, FIGS. 5A and 5B illustrate alternative processes of forming afuran-containing FR molecule from renewable furfuryl alcohol. In theexamples of FIGS. 5A and 5B, furfuryl alcohol is used to form afuran-containing FR molecule having a single furan moiety bonded to aphosphorus moiety via a phosphinyl linkage. As described further herein,the phosphorus moiety includes a chloride group for bonding (e.g., viachemical reaction with a hydroxyl group), and the single furan moietyprovides one potential location for a Diels-Alder reaction with adienophile group of another material.

FIGS. 6-10 illustrate example applications of the furan-containing FRmolecules depicted in FIG. 1. In some cases, as illustrated anddescribed further herein with respect to FIGS. 6-9, the furan-containingFR molecules of the present disclosure may be utilized to form a CLFRpolymer with terminal furan groups. The terminal furan groups act asdienes and will react with a polymeric material that is functionalizedwith dienophile groups. An illustrative, non-limiting example of adienophile includes a succinimide or succinic anhydride-functionalizedpolymer, and the resulting cross-linking reaction can be renderedreversible under specific thermal conditions.

In other cases, as illustrated and described further herein with respectto FIG. 10, the furan-containing FR molecules of the present disclosuremay be utilized to form a cross-linkable flame retardant particle(CLFRP) having diene functionality. In some cases, the CLFRP may beblended with a matrix polymer that contains dienophiles such as asuccinic anhydride-functionalized polymer. The resulting cross-linkingreaction can be rendered reversible under specific thermal conditions.As another example, FIG. 11 illustrates that the CLFRP of FIG. 10 may bereacted with a corresponding dienophile-modified particle via aDiels-Alder reaction. The reaction may be rendered reversible underspecific thermal conditions.

Referring to FIG. 6, a chemical reaction diagram 600 illustrates aparticular embodiment of a process of utilizing the firstfuran-containing FR molecule depicted in FIG. 1 to form a CLFRpolymeric/oligomeric material.

The first chemical reactions depicted at the top of FIG. 6 illustratesthat furan dicarboxylic methyl ester (FDME) may be used to form apolymeric backbone. In some embodiments, FDME may be produced fromrenewable resource-derived fructose, thereby increasing the renewablecontent. The second chemical reaction depicted at the bottom of FIG. 6illustrates that the first furan-containing FR molecule of FIG. 1 may beused to form a CLFR polymeric/oligomeric material with two terminalfuran groups (on each end of the polymer chain). The firstfuran-containing FR molecule of FIG. 1 may be bound to the terminal endsof the polymeric backbone via a chemical reaction of the chloride groupand a hydroxyl group.

As a prophetic example, FDME may be added to an aqueous solution of KOH(3M), and stirred vigorously at 80° C. The reaction may also contain anorganic solvent such as THF, and heated to reflux. Upon completion, thereaction mixture may be cooled to room temperature, and extracted withdiethyl ether. The combined aqueous layers may be acidified with anaqueous acid such as 3M HCl, and extracted with diethyl ether. Thesolvents may be removed in vacuo and the crude product may be purifiedby recrystallization. Subsequently, magnesia (excess) may be added to amixture of alkyl dichlorophosphate, aryl dichlorophosphate, alkyldichlorophosphine oxide, or aryl dichlorophosphine oxide (1.0 eq.) andthe carboxylic acid (1.01-1.20 eq.). This mixture may be stirred at roomtemperature for 5-30 minutes. The solid mixture may be washed withdichloromethane (4×25). The solution may be washed subsequently withsaturated NaHCO₃(aq.), brine, and dried over MgSO₄. The solvent may beremoved in vacuo, and the crude product purified by any combination ofrecrystallization, re-precipitation, or chromatography. Magnesia(excess) may be added to a mixture of first furan-containing FR molecule(1.0 eq.) and the carboxylic acid-termined CLFR material (1.01-1.20eq.). This mixture may be stirred at room temperature, heated up to 150°C., or be performed in an organic solvent such as THF, dioxane, or DMFfor 5-30 minutes. The solid mixture may be washed with dichloromethane(4×25). The solution may be washed subsequently with saturatedNaHCO₃(aq.), brine, and dried over MgSO₄. The solvent may be removed invacuo, and the crude product purified by any combination ofrecrystallization, re-precipitation, or chromatography.

The CLFR polymeric material of FIG. 6 may subsequently be used as aDiels-Alder active cross-linker where the two terminal furan groups (oneach end of the polymer) act as dienes and may react with polymericmaterials functionalized with dienophile functional group(s). Forexample, a dienophile such as a succinimide-functionalized polymer or asuccinic anhydride-functionalized polymer may be used, and the resultingcross-linking reaction can be rendered reversible under specific thermalconditions. The furan groups in the CLFR backbone do not react understandard Diels-Alder reaction conditions as they are deactivated(electron-deficient) due to the flanking carbonyl groups. Thus, only theterminal furan groups react under standard Diels-Alder reactionconditions.

Thus, FIG. 6 illustrates an example of a process of utilizing afuran-containing FR molecule of the present disclosure to form across-linkable flame retardant polymeric material. In the example ofFIG. 6, the CLFR polymeric material includes two terminal furan groups(on each end of the polymer chain). The terminal furan groups representdiene groups that provide two potential cross-linking locations forreaction with dienophile functional groups of another polymericmaterial.

Referring to FIG. 7, a chemical reaction diagram 700 illustrates aparticular embodiment of a process of utilizing the secondfuran-containing FR molecule depicted in FIG. 1 to form a CLFRpolymeric/oligomeric material.

The first chemical reactions depicted at the top of FIG. 7 illustratethat FDME may be used to form a polymeric backbone. In some embodiments,FDME may be produced from renewable resource-derived fructose. Thesecond chemical reaction depicted at the bottom of FIG. 7 illustratesthat the second furan-containing FR molecule of FIG. 1 may be used toform a CLFR polymeric/oligomeric material with one terminal furan group(on each end of the polymer). The second furan-containing FR molecule ofFIG. 1 may be bound to the terminal ends of the polymeric backbone via achemical reaction of the chloride group and a hydroxyl group.

As a prophetic example, CLFR (2) of FIG. 7 may be prepared in a similarfashion to CLFR (1) of FIG. 6, in which the second furan-containingmolecule may be substituted for the first furan-containing moleculeduring the third and final reaction step (addition offuran-functionalized phosphorous-based end groups of thepolymer/oligomer).

The CLFR polymeric material of FIG. 7 may subsequently be used as aDiels-Alder active cross-linker where the terminal furan group (on eachend of the polymer) acts as a diene and may react with polymericmaterials functionalized with dienophile functional group(s). Forexample, a dienophile such as a succinimide-functionalized polymer or asuccinic anhydride-functionalized polymer may be used, and the resultingcross-linking reaction can be rendered reversible under specific thermalconditions. The furan groups in the CLFR backbone do not react understandard Diels-Alder reaction conditions as they are deactivated(electron-deficient) due to the flanking carbonyl groups. Thus, only theterminal furan group reacts under standard Diels-Alder reactionconditions.

Thus, FIG. 7 illustrates an example of a process of utilizing afuran-containing FR molecule of the present disclosure to form across-linkable flame retardant polymeric material. In the example ofFIG. 7, the CLFR polymeric material includes one terminal furan group(on each end of the polymer chain). The terminal furan group representsa diene group that provides a potential cross-linking location forreaction with a dienophile functional group of another polymericmaterial.

Referring to FIG. 8, a chemical reaction diagram 800 illustrates aparticular embodiment of a process of utilizing the thirdfuran-containing FR molecule depicted in FIG. 1 to form a cross-linkableflame retardant material.

The first chemical reactions depicted at the top of FIG. 8 illustratethat FDME may be used to form a polymeric backbone. In some embodiments,FDME may be produced from renewable resource-derived fructose. Thesecond chemical reaction depicted at the bottom of FIG. 7 illustratesthat the third furan-containing FR molecule of FIG. 1 may be used toform a CLFR polymeric/oligomeric material with two terminal furan groups(on each end of the polymer chain). The third furan-containing FRmolecule of FIG. 1 may be bound to the terminal ends of the polymericbackbone via a chemical reaction of the chloride group and a hydroxylgroup.

As a prophetic example, CLFR (3) of FIG. 8 may be prepared in a similarfashion to CLFR (1) of FIG. 6, in which the second furan-containingmolecule may be substituted for the first furan-containing moleculeduring the third and final reaction step (addition offuran-functionalized phosphorous-based end groups of thepolymer/oligomer).

The CLFR polymeric material of FIG. 8 may subsequently be used as aDiels-Alder active cross-linker where the two terminal furan groups (oneach end of the polymer) act as dienes and may react with polymericmaterials functionalized with dienophile functional group(s). Forexample, a dienophile such as a succinimide-functionalized polymer or asuccinic anhydride-functionalized polymer may be used, and the resultingcross-linking reaction can be rendered reversible under specific thermalconditions. The furan groups in the CLFR backbone do not react understandard Diels-Alder reaction conditions as they are deactivated(electron-deficient) due to the flanking carbonyl groups. Thus, only theterminal furan groups react under standard Diels-Alder reactionconditions.

Thus, FIG. 8 illustrates an example of a process of utilizing afuran-containing FR molecule of the present disclosure to form across-linkable flame retardant polymeric material. In the example ofFIG. 8, the CLFR polymeric material includes two terminal furan groups(on each end of the polymer chain). The terminal furan group representsa diene group that provides a potential cross-linking location forreaction with a dienophile functional group of another polymericmaterial.

Referring to FIG. 9, a chemical reaction diagram 900 illustrates aparticular embodiment of a process of utilizing the fourthfuran-containing FR molecule depicted in FIG. 1 to form a cross-linkableflame retardant material.

The first chemical reactions depicted at the top of FIG. 9 illustratethat FDME may be used to form a polymeric backbone. In some embodiments,FDME may be produced from renewable resource-derived fructose. Thesecond chemical reaction depicted at the bottom of FIG. 9 illustratesthat the fourth furan-containing FR molecule of FIG. 1 may be used toform a CLFR polymeric/oligomeric material with one terminal furan group(on each end of the polymer). The fourth furan-containing FR molecule ofFIG. 1 may be bound to the terminal ends of the polymeric backbone via achemical reaction of the chloride group and a hydroxyl group.

As a prophetic example, CLFR (4) of FIG. 9 may be prepared in a similarfashion to CLFR (1) of FIG. 6 in which the second furan-containingmolecule may be substituted for the first furan-containing moleculeduring the third and final reaction step (addition offuran-functionalized phosphorous-based end groups of thepolymer/oligomer).

The CLFR polymeric material of FIG. 9 may subsequently be used as aDiels-Alder active cross-linker where the terminal furan group (on eachend of the polymer) acts as a diene and may react with polymericmaterials functionalized with dienophile functional group(s). Forexample, a dienophile such as a succinimide-functionalized polymer or asuccinic anhydride-functionalized polymer may be used, and the resultingcross-linking reaction can be rendered reversible under specific thermalconditions. The furan groups in the CLFR backbone do not react understandard Diels-Alder reaction conditions as they are deactivated(electron-deficient) due to the flanking carbonyl groups. Thus, only theterminal furan group reacts under standard Diels-Alder reactionconditions.

Thus, FIG. 9 illustrates an example of a process of utilizing afuran-containing flame retardant molecule of the present disclosure toform a cross-linkable flame retardant material. In the example of FIG.9, the CLFR polymeric material includes one terminal furan group (oneach end of the polymer chain). The terminal furan group represents adiene group that provides a potential cross-linking location forreaction with a dienophile functional group of another polymericmaterial.

FIG. 10 illustrates that the furan-containing FR molecules of thepresent disclosure may be utilized to form a cross-linkable flameretardant particle (CLFRP). In some cases, the CLFRP may be blended witha matrix polymer that contains dienophiles such as a succinicanhydride-functionalized polymer. The resulting cross-linking reactioncan be rendered reversible under specific thermal conditions.Alternatively, FIG. 11 illustrates that the CLFRP of FIG. 10 (or anotherCLFRP formed from another furan-containing FR molecule depicted inFIG. 1) may be reacted with a corresponding dienophile-modified particlevia a Diels-Alder reaction. The reaction may be rendered reversibleunder specific thermal conditions.

Referring to FIG. 10, a chemical reaction diagram 1000 shows aparticular embodiment of a process of utilizing the firstfuran-containing FR molecule depicted in FIG. 1 to form a CLFRP. It willbe appreciated that the other furan-containing FR molecules depicted inFIG. 1 may also be utilized to form corresponding CLFRPs. Thus, FIG. 10depicts a non-limiting, illustrative example of a CLFRP that may beformed from one of the furan-containing FR molecules of the presentdisclosure.

In FIG. 10, a furan-containing FR molecule is chemically reacted with asurface of a hydroxyl-containing particle (e.g., a silica particlesurface or any reactive filler that has free hydroxyls). Other examplesof hydroxyl-containing particles include glass microbeads, cellulosenanocrystals, cellulose nanofibrils, ZnO or another hydro-containingoxide. In a particular embodiment, a suspension of silica particles maybe reacted with furan-containing FR molecules to form a CRFP havingdiene functionality.

As a prophetic example, a solution or suspension may be prepared of thehydroxyl-functionalized particles, and an excess of triethylamine (oranother amine based, such as diisopropyl amine, DBU, or DABCO) in anorganic solvent or mixture of organic solvents which be any of thefollowing: toluene, THF, DMF, DMSO, HMPA, NMP, dioxane, ethyl acetate,acetone, DCM, chloroform, chlorobenzene, pyridine, or acetonitrile. Thefirst, second, third, or fourth furan-containing FR molecule may beadded dropwise, and the reaction mixture may be stirred at roomtemperature, heated up to 40-150° C. for 0.5-24.0 hours. The reactionmixture may be cooled to room temperature and subsequently rinsed with1M HCl, and saturated NaHCO₃(aq.), brine, and dried over MgSO₄. Thesolvent may be removed in vacuo, and the crude product purified by anycombination of recrystallization, re-precipitation, or chromatography.

In some cases, the CLFRP of FIG. 10 may be blended with a matrix polymerthat contains dienophiles such as a succinic anhydride-functionalizedpolymer. The resulting cross-linking reaction can be rendered reversibleunder specific thermal conditions. Alternatively, FIG. 11 is a diagram1100 illustrating that the CLFRP of FIG. 10 may be reacted with acorresponding dienophile-modified particle via a Diels-Alder reaction.The reaction may be rendered reversible under specific thermalconditions.

Referring to FIG. 12, a flow diagram illustrates an example of a process1200 of forming a CLFR polymeric material from a furan-containing flameretardant molecule. It will be appreciated that the operations shown inFIG. 12 are for illustrative purposes only and that the operations maybe performed in alternative orders, at alternative times, by a singleentity or by multiple entities, or a combination thereof. As an example,one entity may form the furan-containing FR molecule from the furfurylalcohol (depicted as operation 1202 in FIG. 12), while another entitymay form a polymeric backbone from FDME (depicted as operation 1204 inFIG. 12), while yet another entity may chemically react thefuran-containing FR molecule with the polymeric backbone formed fromFDME to form the CLFR polymeric material (depicted as operation 1206 inFIG. 12).

The process 1200 includes forming a furan-containing FR molecule fromfurfuryl alcohol, at 1202. The FR furan-containing molecule includes afuran moiety bonded to a phosphorus moiety via a phosphoryl linkage or aphosphinyl linkage. For example, the first FR furan-containing moleculedepicted in FIG. 1 (e.g., a difuran-functionalized phosphate material)may be formed from furfuryl alcohol according to the process describedherein with respect to FIG. 2. As another example, the secondfuran-containing FR molecule depicted in FIG. 1 (e.g., amonofuran-functionalized phosphate material) may be formed from furfurylalcohol according to one of the processes described herein with respectto FIGS. 3A and 3B. As a further example, the third furan-containing FRmolecule depicted in FIG. 1 (e.g., a difuran-functionalized phosphineoxide material) may be formed from furfuryl alcohol according to one ofthe processes described herein with respect to FIGS. 4A and 4B. As yetanother example, the fourth furan-containing FR molecule depicted inFIG. 1 (e.g., a monofuran-functionalized phosphonate material) may beformed from furfuryl alcohol according to one of the processes describedherein with respect to FIGS. 5A and 5B.

The process 1200 includes forming a first polymeric material from FDME,at 1204. For example, referring to FIGS. 6-9, FDME may be utilized toform a polymeric backbone with terminal carboxylic acid groups forsubsequent reaction with the furan-containing FR molecules of thepresent disclosure. In some cases, FDME may be derived from renewablefructose, thereby increasing renewable content.

The process 1200 includes chemically reacting the furan-containing FRmolecule with the polymeric material formed from FDME to form a CLFRpolymeric material, at 1206. For example, referring to FIG. 6, theFDME-derived polymeric material may be chemically reacted with the firstfuran-containing FR molecule of FIG. 1 (a difuran-functionalizedphosphate molecule) to form the first CLFR polymeric material (havingtwo terminal furan groups on each end of the polymer). A chemicalreaction between the chloride group of the first furan-containing FRmolecule and a terminal hydroxyl group may bind the firstfuran-containing FR molecule to the FDME-derived material. As anotherexample, referring to FIG. 7, the FDME-derived polymeric material may bechemically reacted with the second furan-containing FR molecule of FIG.1 (a monofuran-functionalized phosphate molecule) to form the secondCLFR polymeric material (having one terminal furan group on each end ofthe polymer). A chemical reaction between the chloride group of thesecond furan-containing FR molecule and a terminal hydroxyl group maybind the second furan-containing FR molecule to the FDME-derivedmaterial. As a further example, referring to FIG. 8, the FDME-derivedpolymeric material may be chemically reacted with the thirdfuran-containing FR molecule of FIG. 1 (a difuran-functionalizedphosphine oxide molecule) to form the third CLFR polymeric material(having two terminal furan groups on each end of the polymer). Achemical reaction between the chloride group of the thirdfuran-containing FR molecule and a terminal hydroxyl group may bind thethird furan-containing FR molecule to the FDME-derived material. As yetanother example, referring to FIG. 9, the FDME-derived polymericmaterial may be chemically reacted with the fourth furan-containing FRmolecule of FIG. 1 (a monofuran-functionalized phosphonate molecule) toform the fourth CLFR polymeric material (having one terminal furan groupon each end of the polymer). A chemical reaction between the chloridegroup of the fourth furan-containing FR molecule and a terminal hydroxylgroup may bind the fourth furan-containing FR molecule to theFDME-derived material.

Thus, FIG. 12 illustrates an example of a process of utilizing thefuran-containing flame retardant molecules of the present disclosure andan FDME-derived material to form a CLFR polymeric material. FIG. 12illustrates that the CLFR polymeric material may include one or moreterminal furan groups on each end of the polymer, providing the abilityto vary a degree of subsequent cross-linking (e.g., with anotherpolymeric material, such as another renewable polymeric material or anon-renewable polymeric material).

Referring to FIG. 13, a flow diagram illustrates an example of a process1300 of forming a cross-linkable flame retardant particle (CLFRP) from afuran-containing FR molecule. In the particular embodiment depicted inFIG. 13, the process 1300 further includes reversibly cross-linking theCLFR particle to another material that is functionalized with adienophile group (e.g., a dienophile-functionalize polymeric material ora dienophile-functionalized particle). It will be appreciated that theoperations shown in FIG. 13 are for illustrative purposes only and thatthe operations may be performed in alternative orders, at alternativetimes, by a single entity or by multiple entities, or a combinationthereof. As an example, one entity may form the furan-containing FRmolecule from the furfuryl alcohol (depicted as operation 1302 in FIG.13), while another entity may utilize the furan-containing FR moleculeto form the CLFRP (depicted as operation 1304 in FIG. 13), while yetanother entity may reversibly bond the CLFRP to adienophile-functionalized material via a Diels-Alder reaction (depictedas operation 1306 in FIG. 13).

The process 1300 includes forming a furan-containing FR molecule fromfurfuryl alcohol, at 1302. The furan-containing FR molecule includes afuran moiety bonded to a phosphorus moiety via a phosphoryl linkage or aphosphinyl linkage. For example, the first furan-containing FR moleculedepicted in FIG. 1 (e.g., a difuran-functionalized phosphate material)may formed according to the process described herein with respect toFIG. 2. As another example, the second furan-containing FR moleculedepicted in FIG. 1 (e.g., a monofuran-functionalized phosphate material)may be formed according to one of the processes described herein withrespect to FIGS. 3A and 3B. As a further example, the thirdfuran-containing FR molecule depicted in FIG. 1 (e.g., adifuran-functionalized phosphine oxide material) may be formed accordingto one of the processes described herein with respect to FIGS. 4A and4B. As yet another example, the fourth furan-containing FR moleculedepicted in FIG. 1 (e.g., a monofuran-functionalized phosphonatematerial) may be formed according to one of the processes describedherein with respect to FIGS. 5A and 5B.

The process 1300 includes chemically reacting the FR furan-containingmolecule with a hydroxyl-containing particle (e.g., a silica particle)to form a CLFRP, at 1304. For example, referring to FIG. 10, the silicaparticle may be chemically reacted with the first furan-containing FRmolecule of FIG. 1 to form the CLFRP. While not shown in the example ofFIG. 10, similar chemical reactions may occur between ahydroxyl-containing particle (e.g., a silica particle) and the otherfuran-containing FR particles depicted in FIG. 1.

The process 1300 further includes reversibly cross-linking the CLFRP toa dienophile-functionalized material via a Diels-Alder reaction, at1306. For example, referring to FIG. 11, the CLFRP of FIG. 10 may bereversibly bonded to a dienophile-functionalized particle (e.g., adienophile-functionalized silica particle) via a Diels-Alder reaction.Alternatively, while not shown in the example of FIG. 11, the CLFRP ofFIG. 10 may be reversibly bonded to a polymeric material that includesdienophile functional groups.

Thus, FIG. 13 illustrates an example of a process of utilizing thefuran-containing FR molecules of the present disclosure to form a CLFRparticle. The furan moieties bonded to the CLFRP provide availablelocation(s) for reversible cross-linking with another material thatincludes dienophile functional groups.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

What is claimed is:
 1. A flame retardant molecule having the followingchemical structure:

wherein X corresponds to a 2-methylfuran group, an alkyl group, or aphenyl group.
 2. The flame retardant molecule of claim 1, wherein Xcorresponds to a 2-methylfuran group, the flame retardant moleculeformed from an intermediate molecule having the following chemicalstructure:


3. The flame retardant molecule of claim 2, wherein the flame retardantmolecule is formed via a chemical reaction of the intermediate moleculewith isocyanuric chloride.
 4. The flame retardant molecule of claim 2,wherein the flame retardant molecule is formed via a chemical reactionof the intermediate molecule with tert-butyl hypochlorite.
 5. The flameretardant molecule of claim 1, wherein X corresponds to an alkyl group,the flame retardant molecule formed via a chemical reaction of furfurylalcohol with an alkyl dichlorophosphate molecule.
 6. The flame retardantmolecule of claim 5, wherein the alkyl group is an ethyl group, a methylgroup, a propyl group, or an isopropyl group.
 7. The flame retardantmolecule of claim 1, wherein X corresponds to a phenyl group, the flameretardant molecule formed via a chemical reaction of furfuryl alcoholwith a phenyl dichlorophosphate molecule.
 8. The flame retardantmolecule of claim 1, wherein X corresponds to an alkyl (R) group, theflame retardant molecule formed from an intermediate molecule having thefollowing chemical structure:


9. The flame retardant molecule of claim 8, wherein the alkyl (R) groupis an ethyl group, a methyl group, a propyl group, or an isopropylgroup.
 10. The flame retardant molecule of claim 1, wherein Xcorresponds to a phenyl group, the flame retardant molecule formed froman intermediate molecule having the following chemical structure:


11. A flame retardant molecule having the following chemical structure:


12. The flame retardant molecule of claim 11, formed from anintermediate molecule having the following chemical structure:


13. The flame retardant molecule of claim 11, formed from anintermediate molecule having the following chemical structure:


14. A flame retardant molecule having the following chemical structure:

wherein R corresponds to an alkyl group or a phenyl group.
 15. The flameretardant molecule of claim 14, formed from an intermediate moleculehaving the following chemical structure:


16. The flame retardant molecule of claim 14, formed from anintermediate molecule having the following chemical structure:


17. The flame retardant molecule of claim 14, wherein R corresponds toan alkyl group selected from the group consisting of: an ethyl group, amethyl group, a propyl group, and an isopropyl group.
 18. The flameretardant molecule of claim 1, derived from furfuryl alcohol.
 19. Theflame retardant molecule of claim 11, derived from furfuryl alcohol. 20.The flame retardant molecule of claim 14, derived from furfuryl alcohol.